No, my web site is not up to date. Using the dimensions of the real abby as well as the paramters of the drivers gives funny frequency response in the calculation sheet. I tried to make a compromise between the ideal box and the shape of the real Abby. BUT, my current listening test show me that there is not a big different in musicality between the "ideal" box and the real Abby box. I will stick to that design and publish the results on the web. Yesterday I did some measurement using my microphone and found that it was really good. A bit of exageration (few db) in the mid-range but no major problem.
I have put more details on my web page, enjoy 
Here are the measurements...
Here are the measurements...
An externally hosted image should be here but it was not working when we last tested it.
Nelson Pass said:
This is a good question. Like the previous people are mentionning, this could be a room mode because the measurements have been made at the listening position. Unfortunatelly I can not do the measurement outside of the house because this is winter here
It could also be related to what MJK is mentionning. I could add some absorbing material on the floor and compare. I tried the exact same BSC of MJK project (FE164E) and the results were really bad, it completely destroyed the mid-range so now there is no crossover, this is more zen
My measurement setup is a behringer ECM8000 + Apex mic preamp + trueRTA and I was using an ASL wave 8 as the amp. The results are pretty much the same with my Zen V4.
Let me know if you have any suggestion
Measurements are only one part of the picture.
How do they sound? If you are happy with the performance then who cares how they measure.
If you are not happy with the performance then do they sound like they measure? Probably weak bass and dominant midrange and high end. If this is the case then you need to take some corrective actions.
My guess is that you will never solve the deep nulls. But a reworked BSC filter might help with the rebalancing of the SPL resposne. I am not sure what filter you tried and discarded.
How do they sound? If you are happy with the performance then who cares how they measure.
If you are not happy with the performance then do they sound like they measure? Probably weak bass and dominant midrange and high end. If this is the case then you need to take some corrective actions.
My guess is that you will never solve the deep nulls. But a reworked BSC filter might help with the rebalancing of the SPL resposne. I am not sure what filter you tried and discarded.
I tried your BSC Martin (http://www.quarter-wave.com/Project02/Parts_List.pdf)!!
They sound great actually. Yes the mid is more present but the tonal balance is not so bad and I enjoy very much listening to them. I found they are sounding better on tube amp then my Zen but I guess I will have to build a more appropriate Zen
They sound great actually. Yes the mid is more present but the tonal balance is not so bad and I enjoy very much listening to them. I found they are sounding better on tube amp then my Zen but I guess I will have to build a more appropriate Zen
cheers T.C.
Now I am really confused. First Frank DIY wrote :
Not so bad? That is a long way from "Great!".
Did you try making adjustments to the circuit? That particular circuit was the one that worked well in my room, with my amp, and my personal taste in bass/midrange response. A 1 ohm change in the parallel resistor makes a significant change in the SPL response. With a tube amp (low damping factor) the resistor value should be much less then what I used for my 200 watt SS amp (high damping factor) in Project #2.
You can also increase or decrease the inductor value to shift the transition frequency up (smaller value) or down (larger value).
You have to tweak the circuit to mesh with your particular situation. I bet if you revisited the circuit and tried a few lower values of resistance and maybe a smaller inductor you might find that the sound inproves over what you have without a BSC circuit.
The only way this might not work out is if you have a low power tube amp which just runs out of steam. Have you tried a higher power SS amp and with the original circuit?
Again, you have to tweak the BSC circuit component values to get the optimum response for your situation. The choice is yours, if you are happy and satisfied with the current performance that is all that matters. Personally, I see room for improvement after seeing that SPL plot. I lived with a similar plot for a while.
Not so bad? That is a long way from "Great!".
Did you try making adjustments to the circuit? That particular circuit was the one that worked well in my room, with my amp, and my personal taste in bass/midrange response. A 1 ohm change in the parallel resistor makes a significant change in the SPL response. With a tube amp (low damping factor) the resistor value should be much less then what I used for my 200 watt SS amp (high damping factor) in Project #2.
You can also increase or decrease the inductor value to shift the transition frequency up (smaller value) or down (larger value).
You have to tweak the circuit to mesh with your particular situation. I bet if you revisited the circuit and tried a few lower values of resistance and maybe a smaller inductor you might find that the sound inproves over what you have without a BSC circuit.
The only way this might not work out is if you have a low power tube amp which just runs out of steam. Have you tried a higher power SS amp and with the original circuit?
Again, you have to tweak the BSC circuit component values to get the optimum response for your situation. The choice is yours, if you are happy and satisfied with the current performance that is all that matters. Personally, I see room for improvement after seeing that SPL plot. I lived with a similar plot for a while.
What you gain in flat response, you will loose in "dynamics, tone and transparency" adding such circuitry. Unless you sneak around the absorption and impedance effects these have on signals, amps etc. and use current source amp. "D_T_and T". Everything is a tradeoff. He's already traded some acoustic chips for good tone by using a low watt tube amp. I bet it sounds great.
The dip could well be positioning. (ok it is also his pointy top) .
Bringing the speakers closer together always results in better midbass in any room. Imagery densifies and I bet measurements would prove it
TC
Let me recap...
They sound great. I mostly listen to jazz music and to me, I don't want to add a crossover. The only thing I might tweak in the future is the damping. I want also to keep the efficiency as high as possible.
Based on your comments, I will try to do other measurements soon (different positionning and I will try to reduce the room effect).
They sound great. I mostly listen to jazz music and to me, I don't want to add a crossover. The only thing I might tweak in the future is the damping. I want also to keep the efficiency as high as possible.
Based on your comments, I will try to do other measurements soon (different positionning and I will try to reduce the room effect).
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